Add container classes as utilities not components

Just for now so that this feature can be introduced into the codebase
without forcing a BC break. The container classes will eventually be
moved to a built-in plugin that adds them as components.

Author: adamwathan

__tests__/fixtures/tailwind-input.css

@@ -1,7 +1,5 @@
 @tailwind preflight;
 
-@tailwind components;
-
 @tailwind utilities;
 
 @responsive {

src/lib/substituteTailwindAtRules.js

@@ -21,20 +21,12 @@ export default function(config) {
       }
 
       if (atRule.params === 'components') {
-        const tailwindComponentTree = postcss.root({
-          nodes: container(unwrappedConfig),
-        })
-
         const pluginComponentTree = postcss.root({
           nodes: pluginComponents,
         })
 
-        prefixTree(tailwindComponentTree, unwrappedConfig.options.prefix)
-
-        tailwindComponentTree.walk(node => (node.source = atRule.source))
         pluginComponentTree.walk(node => (node.source = atRule.source))
 
-        atRule.before(tailwindComponentTree)
         atRule.before(pluginComponentTree)
         atRule.remove()
       }
@@ -47,7 +39,7 @@ export default function(config) {
         }
 
         const tailwindUtilityTree = postcss.root({
-          nodes: utilities.nodes,
+          nodes: [...container(unwrappedConfig), ...utilities.nodes],
         })
 
         const pluginUtilityTree = postcss.root({